In a fluidized bed reaction, in general, a reactive gas is supplied from a lower part of a reactor filled with a catalyst and catalyst particles are fluidized by the gas flow in the reactor, and then the catalyst particles are contacted with the reactive gas to allow the reaction to proceed. Here, the catalyst used for the fluidized bed reaction is required to have physical properties suitable for the fluidized bed reaction such as chemical performance, particle shape, size, distribution, fluidity and strength.
There is described a suitable property of catalyst particles for achieving a preferable fluidized state in the fluidized bed reaction step, for example, in page 16 of “Fluidized Bed Handbook” (edited by the Association of Powder Process Industry & Engineering, Japan, and published by Baifukan on Mar. 25, 1999). The document describes: “A sufficiently fast mass transfer between gas bubbles and an emulsion phase containing a catalyst is preferable in improving the reaction rate and selection rate. For this purpose, smaller gas bubbles are preferable and it is considered to be preferable that the particles are small and have a smooth and slippery surface. And, it is generally said that preferred particles have a bulk density of 0.6 to 1.0 g·cm−3 and an average diameter of 60 to 80 μm.” In addition, if there occurs attrition or fracture of catalyst particles due to collision or contact between catalyst particles, between catalyst particles and the reactor, and between the catalyst particles and the reactive gas, accompanied by the fluidization of the catalyst, the fluidity of catalyst particles is decreased and fractured particles are scattered. Consequently, as the property of the fluidized bed reaction catalyst, mechanical strength sufficiently enough to withstand attrition or fracture is also demanded.
That is, a catalyst used for a fluidized bed reaction is required to have a shape, a particle size distribution and the like excellent in fluidity, and mechanical strength (attrition resistance) to withstand collision or contact between catalyst particles, between catalyst particles and the reactor, and between the catalyst particles and the reactive gas.
In order that the catalyst has mechanical strength suitable for the fluidized bed reaction, there is known a method in which a catalyst active component such as zeolite is molded with a support component which becomes a binder such as alumina, silica and clay, and the molded product is calcined. For example, in Patent Document 1, there is described a method in which a buffered silica sol is prepared by adding sulfuric acid and aluminum sulfate to sodium silicate, and to the buffered silica sol are added clay and zeolite to prepare a raw material slurry which is adjusted to a specific pH, followed by spray drying the slurry to produce a hydrocarbon conversion catalyst having high attrition resistance. In addition, in Patent Document 2, there is disclosed a production method of a fluidized catalytic cracking catalyst in which the catalyst is a fluidized bed catalyst with meso-porosity comprising zeolite, gibbsite (aluminum hydroxide), a rare earth metal and a silica matrix, and the silica matrix is prepared from a silica sol prepared by an ion exchange method or from an acidic silica sol containing sodium silicate, sulfuric acid and aluminum sulfate.    [Patent Document 1] Japanese Patent Application Laid-Open No. 51-40390    [Patent Document 2] Japanese Patent Application Laid-Open No. 10-146529